In Europe, the period of great economic and demographic growth is largely over. The physical growth of our urban agglomerations has come to an end. The spatial assignment of the future European city will be fundamentally different. Building new space outside the city boundaries is no longer necessary. Instead, what exists should be made sustainable. The new spatial assignment involves maintaining, restructuring, densifying or diluting the existing city. This publication analyses this development and describes a toolbox that is able to turn the new assignment into a success.